1. Field of the Invention
The present invention relates to an endoscopic system adopting a solid-state camera element, and particularly to an endoscopic system which can provide excellent real-time images and frozen images.
2. Description of the Prior Art
Conventionally, in a kind of endoscopic system, an object to be photographed is irradiated by continuous light or by pulsed light to obtain real-time images or frozen images of the object, respectively.
If the object is irradiated by the continuous light to obtain a frozen image thereof, a blur may be caused in the obtained frozen image. Therefore, the pulsed light is usually used for obtaining a frozen image having no blur. As shown in FIG. 1, the pulsed light is irradiated onto the object in synchronism with the field shift timing of a solid-state camera element. Electric charge of the solid-state camera element is transferred at the timing of, for instance, a 1/60 second interval corresponding to a field shifting rate shown in FIG. 1. In synchronizing with the intervals of respective fields A, B, C, D, E, F, and so on to be shifted, the pulsed light is emitted repeatedly.
When pulsed light of type "A" shown in FIG. 1 is used to obtain real-time images, the obtained images may be continuous with 1/60 second intervals and not intermittent. However, when the pulsed light of type "A" is used to obtain a frozen image, the image will not successfully be frozen because there is a time difference of 1/60 second between an image of the field "A" and an image of the field "B". When pulsed light of type "B" shown in FIG. 1 is used, a good frozen image of one frame may be obtained, but good real-time images may not be obtained with the same pulsed light of type "B". This is because a time difference between an image of the field "D" and an image of the field "E" is "L" which is larger than 1/60 second to deteriorate continuity in the real-time images. Namely, when the real-time images by the light of type "B" are displayed on a monitoring display screen such as a CRT, the images will not be continuous but intermittent.
As described in the above, the continuous light irradiation will cause a blur in a frozen image, and the pulsed light irradiation will cause problems that a frozen image of a frame may not successfully be obtained from a quickly moving object and that real time images on a monitoring display screen such as a CRT are not continuous but intermittent. Therefore, it causes an unnatural feeling to an operator who is monitoring the images.